package ch15;

/**
 * Created by 春旺 on 2017/10/13.
 */
public interface Queue<T>
{
    // Adds the specified element to the rear of the queue.
    public void enqueue (T element);
    // Removes and returns the element at the front of the queue.
    public T dequeue();
    // Returns a reference to the element at the front of the queue
// without removing it.
    public T first();
    // Returns true if the queue contains no elements and false
// otherwise.
    public boolean isEmpty();
    // Returns the number of elements in the queue.
    public int size();
    // Returns a string representation of the queue.
    public String toString();
}
